Most topical antiperspirant products available today contain antiperspirant actives such as zirconium and aluminum salts, most typically in their enhanced form (e.g., improved or activated antiperspirant active). These enhanced aluminum and zirconium salts are formulated into topical products as either suspended particulate solids or as solubilized or partially solubilized active in an aqueous or alcoholic solvent.
Solubilized, enhanced antiperspirant active can provide a topical product with improved low residue performance and antiperspirant efficacy. These solubilized actives can be formulated into an anhydrous solvent to provide improved dry feel application, antiperspirant efficacy and stability of the dissolved active. Examples of anhydrous solvents commonly used or otherwise known for use in solubilizing these antiperspirant actives include ethylene glycol, diethylene glycol, butylene glycol, 1,2-proplyene glycol, 1,3-propylene glycol, 1,3-butylene glycol (1,3-butane-diol), glycerine (1,2,3-trihydroxy propane), 2-methyl-2,4-pentane-diol (hexylene glycol), 1,2-hexanediol, 2-ethyl-1,3-hexane-diol, 1,2,6-hexanetriol, ethanol, tripropylene glycol, propylene glycol methyl ether, dipropylene glycol methyl ether, and so forth.
Anhydrous compositions containing solubilized, enhanced, antiperspirant active are formulated by any of a variety of known methods. Most of these methods include an initial or intermediate manufacturing step in which aluminum or aluminum-zirconium salts are activated to form improved or enhanced-efficacy antiperspirant active. These activation steps typically involve the application of heat to an aqueous active solution to produce the desired enhanced antiperspirant, followed by the rapid evaporation or removal of water from the heated solution to thus stabilize the enhanced antiperspirant in its improved or enhanced form. The improved or enhanced active contains a higher concentration of lower molecular weight aluminum or aluminum-zirconium polymers making up the active salt. It is believed that the lower molecular weight active polymers provide improved antiperspirant efficacy.
Many variations of the above described method are known for making anhydrous compositions containing solubilized, enhanced, antiperspirant active. One such variation involves the dissolution of enhanced antiperspirant active powder or solids in an aqueous solution containing an anhydrous solvent, followed by the rapid evaporation of water from the enhanced active solution. As with the above-described process, it is important to quickly evaporate the water after dissolution to prevent or minimize the polymeric shift of the enhanced antiperspirant active to a larger, less effective, molecular weight species. It is believed that any such polymeric shift will result in a loss of antiperspirant efficacy.
These methods for making anhydrous compositions containing dissolved enhanced active, however, typically involve a long series of relatively inefficient or costly process steps. For example, many of the prior art methods require an initial series of steps resulting in the formation of spray dried enhanced antiperspirant powder, which is then redissolved in an aqueous solution to begin the next manufacturing sequence. Other methods have avoided this wasteful spray drying-redissolution sequence by making the enhanced antiperspirant active initially in a dilute aqueous solution containing not more than 20% by weight of aluminum active, heating the dilute solution to a temperature of up to 105.degree. C. for several hours to form an enhanced aluminum-containing active, adding an anhydrous solvent, and then rapidly evaporating the water from the solution to form the desired anhydrous composition containing the enhanced aluminum active and the added anhydrous solvent. Although this process avoids the spray drying-redissolution step described above, it requires the use of relative dilute active solutions (not more than 20% by weight of the solution) which then requires substantial amounts of energy during the evaporation sequence to rapidly remove such large amounts of water.
It is therefore an object of the present invention to provide an improved process for making anhydrous compositions containing solubilized, enhanced, antiperspirant actives, wherein the improved process involves a more efficient manufacturing sequence that reduces manufacturing costs, simplifies the manufacturing sequence, and reduces production times.